I haven’t written a post for this blog for a long time, and much has happened. Over the next two months I hope to write at least three posts per week and bring everything up to date. It’s been quite a ride, as you’re about to find out . . .
During the spring and summer of 2014, I spent a couple of hours each week preparing my students for their trip to Caltech for the NASA/IPAC Teacher Archive Research Program (NITARP). “NITARP” is a double-imbedded acronym, with IPAC (the Infrared Processing and Analysis Center) and NASA (National Acronym Slingers Association) as part of it. Our training included how to locate WISE (yes, another one – this is the Wide-field Infrared Survey Explorer) and 2MASS (you might as well get used to it – 2 Micron All-Sky Survey) data and how to combine images taken at different wavelengths into the RGB channels in Adobe Photoshop (much more on this technique later). By the time late July came, the students were ready to go.
We met the students (Elena, Kendall, and Rosie) at Walden School on Monday morning, July 28th and drove to the airport. We flew directly to LAX, where we met up with John Gibbs, Estefania Larson, Elin Deeb, and their students. We caught a shuttle van to the Hertz car lot and rented two SUVs, then drove through Los Angeles to Pasadena on the 110 freeway. Because of my frequent trips down here, I know my way around fairly well. It was an unusually clear day, and I was able to point out the solar telescope domes sticking up on top of Mt. Wilson.
We drove to Dr. Luisa Rebull’s house for an introductory pizza dinner. Kendall and Elena regaled the other students with tales of their expedition to India in June. I’m not sure I ever want to go there after hearing of their nightmare 19-hour train ride that was supposed to be only 10 hours. After the dinner we drove to Pasadena and found our motel, the Comfort Inn on Colorado Blvd. I shared a room with John.
On Tuesday morning we ate breakfast in the Comfort Inn lobby and drove to Caltech, which is located a few blocks south of Colorado Blvd. We parked and walked to the Spitzer Science Center in the Keith Spalding Building off of California Blvd. We began with a tour of the center, seeing where the data link comes in from the Spitzer space telescope. A clock counts the time to the next data downlink, when the spacecraft turns its antenna toward Earth. There was a model of the spacecraft, and Luisa loaded us down with posters and other materials. We also met Wannetta, who handles all the financial arrangements including per diems and travel reimbursements.
The NITARP education center is on the top floor. Luisa introduced our research study and the WISE mission. We are the HG-WELS team, which stands for Hungry Giants: WISE Excess Lithium Study (yeah, I know – it wasn’t my first choice for a name, but at least it is catchy). We are using the WISE, 2MASS, IRAS, and other data sets in the IPAC archives to look at specific K-giant stars that show excess lithium and faster than normal rotation. The idea is that the lithium and rotation may be due to the star ingesting its own planets. The collision of the planet with the star could be providing an angular momentum “kick” to speed up its rotation rate. We theorize that such stars would also show an excess amount of infrared radiation due to a shroud of dust or gas surrounding them as the planet broke apart.
To find this excess IR, we need to create Spectral Energy Distributions (SEDs) for our target stars and look for a “bump” in the WISE, 2MASS, and IRAS data above what one would expect for a normal Raleigh-Jean curve. To create the SEDs, we need to find the log of the flux density (photons per square centimeter per second) for each wavelength and compare it with the logs of the wavelengths. The final axes are logλFλ vs. logλ. This starting point data can be found in the IPAC database and in the SIMBAD catalog, but has to be converted from flux density per frequency to flux density per wavelength.
According to Wien’s Law, each star has a characteristic SED that peaks in a particular wavelength, which is why we say it has a certain spectral classification. O and B stars peak in the ultraviolet and violet wavelengths, a G-type star like our sun peaks in the visible (yellow-green) wavelengths, and an orange or red star, such as the K-giants we are studying, will peak in the red to infrared wavelengths. If it is shrouded in dust or gas, it will show a hump or bump at about the 12 to 46 micron range, right where the WISE data is located.
After this introduction we walked over to the main campus of Caltech past the turtle ponds and Troop Garderns to the cafeteria, which has a large range of types of food. I had the Mongolian barbeque (Meng Gu Kau Rou). We stopped in the bookstore on the way back, and I looked over some hats and other souvenirs but decided to wait until later in the week to buy anything.
In the afternoon we began looking at preliminary data for each star. Luisa had created SEDs for each target and we divided into teams to decide which ones showed the kind of bump we were looking for. Some showed a nice Raleigh-Jean curve, others were very distorted, and some didn’t look like stars at all. As teachers we held telecons all spring and summer to look over the data and had created RBG images using the WISE data. Some of the images looked like galaxies, post AGB stars, protostars, or other exotic objects that were probably not K-giants. Many of these objects had been identified for a previous study using the older IRAS data, which has poor spatial resolution compared with 2MASS and WISE. With the more recent data, we had to decide which objects to throw out and which ones to keep. Another study by Jolene Carlberg used this more recent data and more of her stars appeared to have the pattern we needed.
At 5:00 we finished up going through the 190 or so stars and drove to Old Town Pasadena and parked in a parking garage a block south of Colorado Blvd. We separated into groups and walked around, looking for places to eat. As teachers we found an Indian restaurant that looked promising.
It might have been the same restaurant I ate at back in 1998 that caused me so much trouble, but this time I was careful not to go with any curry dish. Back then, I had been suffering from an intestinal bug that required an antibiotic which wiped out all the beneficial bacteria in my intestines. I was there for the NEWMAST (NASA Educator Workshops for Mathematics And Science Teachers) program, and a group of us found an Indian restaurant in Pasadena. I was finally getting my intestines back in shape when the curry dish totally wiped out everything again, and I had to eat only yogurt for the last two days of the workshop. I’ve avoided curry ever since.
But this time the food was excellent and I didn’t have any side effects. We met up with the students and drove back to the Comfort Inn for the night.